Profiling the Depth and Extent of Contamination of a Ship Channel Using the P450RGS Cell-Based Assay for Dioxins and Related Compounds

A rapid and sensitive cell-based screening assay for dioxin equivalences (TCDD EQs) in dredged sediments has been developed. The P450RGS assay employs a transgenic human hepatoma cell line in which the firefly luciferase gene, luc, has been stably inserted as a reporter. P450RGS conforms to APHA Standard Method 8070 and ASTM Standard E-1853. EPA has promulgated the assay as EPA Method 4425 in update IVA of the EPA SW846 Methods Manual. Modifications to the method made at USACE ERDC-WES include a combined extraction/cleanup procedure using accelerated solvent extraction (ASE) with a sulfuric acid/silica gel packing in the extraction cell, and a 96-well microtiter plate format for the assay. These modifications substantially increase the volume of sample throughput and reduce the cost of the assay. Assays in which TCDD EQs are reported are typically less than 1/10^th the cost of dioxin analysis using GC/MS, and have comparable sensitivity.